Thundering into cloudless blue skies, a United Launch Alliance Atlas V rocket successfully completed its first mission to deploy a Global Positioning System satellite for the Unuted States Air Force. Roaring off the launch pad exactly on time at 5:38 p.m. EDT, Atlas completed its mission three and a half hours later when it deployed GPS IIF-4 into an orbit 11,000 miles above the Earth. This was both the first GPS mission for the Atlas (all previous GPS satellites were launched on Delta II and Delta IV rockets) and the first of two launches scheduled in seven days from Cape Canaveral A.F.S.

“The ULA team is honored to place another next-generation GPS satellite on orbit for our US Air Force customer,” said Jim Sponnick, ULA vice president, Mission Operations. “Today’s successful delivery of the GPS IIF-4 mission represents the 70th launch success in the 77 months since ULA was formed – an accomplishment made possible by seamless integration of the customer and industry team; reliable production and launch operation processes; and a one-launch-at-a-time focus on mission success for these critical space assets.”

This mission was launched aboard an Atlas V 401 EELV with a 4-meter diameter payload fairing. The booster for this mission was powered by the RD AMROSS RD-180 engine and the Centaur upper stage was powered by a single Pratt & Whitney Rocketdyne RL-10A engine.

LIFTOFF! Atlas V with GPS IIF-4. Credit: Val Phillips / Zero-G News

The Atlas V booster is 12.5 ft in diameter and 106.5 ft in length. First stage propulsion is provided by the RD-180 engine system (a single engine with two thrust chambers). The RD-180 burns a highly refined kerosene called RP-1 and liquid oxygen, and delivers 860,200 lb of thrust at sea level. The Atlas V booster is controlled by the Centaur avionics system, which provides guidance, flight control, and vehicle sequencing functions during the booster and Centaur phases of flight.

The Centaur upper stage is 10 ft in diameter and 41.5 ft in length. ICentaur is a cryogenic liquid hydrogen and liquid oxygen fueled vehicle. It uses a single RL10A-4-2 engine producing 22,300 lb of thrust. The forward adapter provides the structural mountings for the fault-tolerant avionics system and the structural and electrical interfaces with the spacecraft.

Credit: NASATech.net

The two-burn mission GPS IIF-4 mission flew a northeasterly trajectory from SLC-41 with a 45.8-degree flight azimuth targeting a final semi-synchronous circular orbit at an altitude of 11,047-nautical miles with a 55-degrees inclination. LThe RD-180 engine roared to life at T-2.72 seconds and ramped up to full power. Liftoff of the vehicle occurred at T+1.1 seconds followed by a pitch/yaw/roll program after clearing the umbilical tower. This maneuver put the rocket on the proper launch azimuth. The Atlas vehicle reached the speed of sound and the region of maximum aerodynamic pressure approximately 90 seconds after launch.

The first-stage shut down about four minutes into flight and separated approximately six seconds later. This was followed by the first ignition of the Centaur ten seconds later. After upper stage ignition, the payload fairing was jettisoned eight seconds later or four minutes and 28 seconds into flight.

Centaur’s engine shut down to complete its first burn at approximately 17 minutes into the mission. This was followed by a three-hour coast phase before the Centaur main engine re-started for a one and one-half minute burn. Fie minutes later the Centaur spun itself up to 5 RPM in preparation for spacecraft separation. The GPS IIF-4 satellite was released from the Centaur second stage at 3 hours and 23 minutes after liftoff

Today’s launch marked the 38th successful launch in a row for the Atlas V rocket which made its debut in 2002.

“The ULA team has launched 51 GPS missions on Delta II and Delta IV vehicles and this mission marks the first operational GPS mission launched on an Atlas V launch vehicle,” said Sponnick. “Successfully and efficiently integrating and launching these satellites on both EELV launch systems provides operational flexibility and in the future, capabilities such as dual launch will provide even greater flexibility and also enable lower launch costs for our customers.”

Climbing away from the pad. Credit: Val Phillips / Zero-G News

GPS IIF-4 is the fourth satellite delivered by prime contractor Boeing as part of the GPS IIF contract for 12 next-generation GPS space vehicles. GPS IIF-4 is the newest in a series of next generation GPS satellites and will join a worldwide timing and navigation system utilizing 24 satellites in six different planes, with a minimum of four satellites per plane positioned in orbit approximately 11,000 miles above the earths’ surface. The GPS IIF series provides improved accuracy and enhanced performance for GPS users.

The Block IIF series will replace the GPS Block IIA satellites that were launched between 1990 and 1997. The IIF space vehicles provide improved accuracy, enhanced internal atomic clocks, better anti-jam resistance, a civil signal for commercial aviation and a longer design life.

For the ULA Atlas V rocket, Alliant Techsystems (ATK) produced the 10-foot diameter composite heat shield, which provides essential protection for the first stage of the launch vehicle. The assembly was fabricated using advanced fiber placement manufacturing techniques at ATK’s Iuka, Miss., facility. This is the 38th Atlas V launch using ATK-built composite structures.

ATK also recently completed qualification of a new retrorocket, and eight of those solid motors supported separation of the spent first stage. The Atlas retrorocket is built at ATK’s Elkton, Md., facility.